Fabrication method of FinFET structure with composite gate helmet

Abstract

A method includes forming gate spacers and a first interlayer dielectric (ILD) layer over a fin structure, forming a metal gate structure between the gate spacers, selectively growing a metal cap on the metal gate structure, depositing a second ILD layer over the metal cap and the first ILD layer, performing a first chemical mechanical polish (CMP) process on the second ILD layer until the metal cap is exposed, replacing the metal cap with a dielectric cap, after replacing the metal cap with the dielectric cap, etching the second and first ILD layers until source/drain regions of the fin structure are exposed, and forming source/drain contacts respectively on the source/drain regions.

What is claimed is: 
     
       1. A method, comprising:
 forming gate spacers and a first interlayer dielectric (ILD) layer over a fin structure; 
 forming a metal gate structure between the gate spacers; 
 selectively growing a metal cap on the metal gate structure; 
 depositing a second ILD layer over the metal cap and the first ILD layer; 
 performing a first chemical mechanical polish (CMP) process on the second ILD layer until the metal cap is exposed; 
 replacing the metal cap with a dielectric cap; 
 after replacing the metal cap with the dielectric cap, etching the second and first ILD layers until source/drain regions of the fin structure are exposed; and 
 forming source/drain contacts respectively on the source/drain regions. 
 
     
     
       2. The method of  claim 1 , wherein selectively growing the metal cap is performed such that the metal cap is laterally grown over top surfaces of the gate spacers. 
     
     
       3. The method of  claim 1 , wherein selectively growing the metal cap is performed such that the metal cap is not grown on a top surface of the first ILD layer. 
     
     
       4. The method of  claim 1 , wherein replacing the metal cap with the dielectric cap comprises:
 etching the metal cap to expose the metal gate structure; 
 depositing a layer of dielectric material on the exposed metal gate structure; and 
 performing a second CMP process on the layer of dielectric material until the second ILD layer is exposed. 
 
     
     
       5. The method of  claim 1 , wherein the dielectric cap remains on the metal gate structure after etching the second and first ILD layers. 
     
     
       6. The method of  claim 1 , wherein forming the source/drain contacts comprises:
 after etching the second and first ILD layers, depositing a layer of metal material on the exposed source/drain regions and the dielectric cap; and 
 performing a second CMP process on the layer of metal material until the dielectric cap is exposed. 
 
     
     
       7. A method, comprising:
 forming a metal gate structure across a fin structure and a protection cap atop the metal gate structure; 
 forming source/drain contacts respectively extending along opposite sides of the protection cap to the fin structure; 
 etching the protection cap to expose sidewalls of the source/drain contacts; 
 forming a gate helmet layer to line a recess defined by the sidewalls of the source/drain contacts and a top surface of the metal gate structure; 
 etching back the source/drain contacts such that top surfaces of the source/drain contacts are lower than a topmost end of the gate helmet layer; and 
 after etching back the source/drain contacts, forming a source/drain via plug on one of the source/drain contacts. 
 
     
     
       8. The method of  claim 7 , wherein forming the gate helmet layer comprises:
 depositing a layer of dielectric material to line the recess defined by the sidewalls of the source/drain contacts and the top surface of the metal gate structure; and 
 performing a chemical mechanical polish (CMP) process on the layer of dielectric material until the source/drain contacts are exposed. 
 
     
     
       9. The method of  claim 7 , wherein forming the source/drain via plug comprises:
 after etching back the source/drain contacts, depositing a liner layer extending along top surfaces of the etched back source/drain contacts and a sidewall of the gate helmet layer; 
 depositing a dielectric layer over the liner layer; 
 performing an etching process to form a via opening through the dielectric layer and the liner layer; and 
 forming the source/drain via plug in the via opening. 
 
     
     
       10. The method of  claim 9 , wherein the liner layer has a greater etch resistance property to the etching process than that of the dielectric layer. 
     
     
       11. The method of  claim 9 , wherein the gate helmet layer remains on the top surface of the metal gate structure after forming the via opening. 
     
     
       12. The method of  claim 9 , wherein the liner layer remains on the sidewall of the gate helmet layer after forming the via opening. 
     
     
       13. The method of  claim 7 , further comprising:
 selectively growing source/drain contact caps on the source/drain contacts, respectively; 
 forming a dielectric structure to fill a recess defined by a top surface of the gate helmet layer and sidewalls of the source/drain contact caps; and 
 after forming the dielectric structure, removing the source/drain contact caps from the source/drain contacts. 
 
     
     
       14. The method of  claim 13 , further comprising:
 forming an alkysilane self-assembled monolayer on the gate helmet layer prior to selectively growing the source/drain contact caps. 
 
     
     
       15. A method, comprising:
 forming a source contact and a drain contact respectively at opposite sides of a metal gate structure; 
 forming a gate helmet extending along a sidewall of the source contact, a top surface of the metal gate structure and a sidewall of a drain contact; 
 forming a source contact cap extending along a top surface of the source contact to beyond an interface between the source contact and the gate helmet, and a drain contact cap extending along a top surface of the drain contact to beyond an interface between the drain contact and the gate helmet; 
 forming a dielectric structure to fill a recess defined by the gate helmet, the source contact cap and the drain contact cap; 
 removing the source contact cap and the drain contact cap to expose opposite sidewalls of the dielectric structure; 
 forming spacers respectively extending along the opposite sidewalls of the dielectric structure; and 
 after forming the spacers, forming a gate via plug extending through top and bottom surfaces of the dielectric structure to the metal gate structure. 
 
     
     
       16. The method of  claim 15 , wherein during forming the source contact cap, the source contact cap is initially grown only on the source contact, and then laterally grown to a position over the gate helmet. 
     
     
       17. The method of  claim 15 , wherein during forming the drain contact cap, the drain contact cap is initially grown only on the drain contact, and then laterally grown to a position over the gate helmet. 
     
     
       18. The method of  claim 15 , further comprising:
 forming an alkysilane self-assembled monolayer on the gate helmet prior to forming the source contact cap and the drain contact cap. 
 
     
     
       19. The method of  claim 15 , wherein forming the dielectric structure comprises:
 depositing a layer of dielectric material into the recess defined by the gate helmet, the source contact cap and the drain contact cap until the source contact cap and the drain contact cap are covered; and 
 performing a chemical mechanical polish (CMP) process on the layer of dielectric material until the source contact cap and the drain contact cap are exposed. 
 
     
     
       20. The method of  claim 15 , further comprising:
 after forming the spacers, etching back the source contact and the drain contact.